JPH02777B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to improved molding compositions, particularly electrically conductive molding compositions capable of producing molded articles with excellent dimensional stability and processability.

Information carriers containing video, audio and color information in the form of microscopic surface roughness patterns on plastic discs are known. The uneven pattern on this surface is monitored with a reproducing needle, and the changes in the surface are reproduced into electrical signals and converted into information suitable for display on a television receiver.

In the method described in US Pat. No. 3,842,194,
It uses a capacitive method, so the disk and the regeneration needle are conductive, with a dielectric layer sandwiched between them. First, a plastic disc is coated with a thin metal film,
The plate is then coated with a dielectric thin film, but the method of forming two thin films is complicated and expensive, and there has been a desire to develop a conductive molding composition that can produce a conductive molded disk.

The volume resistivity at 900MHz is approximately 500Ω-cm or less, preferably 100Ω-
A reproduction of a conductive video disc manufactured by molding a plastic molding composition containing conductive particles sufficiently finely divided to have a particle diameter of less than cm is described; It has been shown that polyvinyl chloride homopolymer or copolymer resins containing conductive particles, lubricants, processing aids, and a sufficient amount of low volume density conductive particles to obtain the required conductivity can be manufactured using Are listed.

The molding composition originally prepared by the inventor of the above-mentioned US patent application was hard and difficult to process, so research was carried out to improve its processability. US Patent No.
No. 4,151,132 describes conductive molding compositions that provide improved processability, less brittle video discs, and regeneration with less additive leaching or staining. Additive leaching or contamination is disadvantageous because it alters the surface characteristics of the video disc, resulting in high noise levels. The process of the above patent overcomes this disadvantage by incorporating a variety of additives, including lubricants, stabilizers and processing aids, in small quantities into the vinyl chloride resin mixture. The composition thus comprises about 12-20% by weight conductive carbon black, about 10% by weight vinyl chloride vinyl acetate copolymer, about 10% by weight vinyl chloride maleate copolymer, about 15-17% by weight % of four or more processing aids and plasticizers, about 3.5% by weight of at least two metal stabilizers, and about 1.5% by weight of at least two
It contains a lubricant of seeds, and the remainder is a vinyl chloride propylene copolymer.

Although these molding compositions can be easily processed and video discs with excellent playback characteristics can be molded, they are disadvantageous in terms of high temperature storage. These compositions have relatively low heat distortion temperatures, resulting in permanent disc deformation or warping and shrinkage when stored above about 37.8°C.

According to recent requirements, conductive molding compositions for video discs form flat rigid discs with excellent reproduction of fine image information that are dimensionally stable when stored at temperatures up to 54.4°C. must be able to do so. The current standard for video discs is 54.4
When stored for 48 hours at °C, vertical deformation or warpage over the entire surface of a 30.5 cm (12 inch) disc is required to be less than 0.05 cm, and lateral shrinkage is required to be less than 0.13 cm. The compositions of the above US patents do not meet this requirement.

As a result, the composition has good processability and thermal stability during processing and molding, and has good replication accuracy of the fine surface unevenness pattern, making it possible to conduct conductive molding with high dimensional stability even when stored under various ambient conditions up to 54.4℃. Research has continued to develop compositions for use.

The inventor of this application claims that at 900MHz approximately 500Ω−
A molding composition capable of producing video disc reproductions with a volume resistivity of less than cm, easy processing, high heat distortion temperature, excellent dimensional stability at 54.4°C and high uniformity and surface properties. discovered. The molding composition contains sufficient fine conductive carbon black particles to provide the required electrical conductivity and approximately
1.5-4% by weight of stabilizers, 1-3% by weight of at least two lubricants, and about 10% or less additive modifiers, but less than about 5% by weight as liquid additives. Contains no polyvinyl chloride resin. Video disc reproductions molded from this composition exhibited excellent resistance to the effects of changes in ambient temperature, humidity, etc.

Due to the special nature of the information on the video disk and its fine dimensions, the composition suitable for molding this disk is one in which conductive particles and other additives are uniformly dispersed in the polyvinyl chloride resin, and the surface of the molded object is It must be free of defects, have little shrinkage or warping, and have a high heat distortion temperature. The composition is also easy to process and can form a fine pattern on the surface of a 12-inch disc, with sufficient additives to overcome the stiffness and brittleness imparted by the large amount of conductive particles it contains. Must be added. However, if the total amount of additives is too high, the additives will leach onto the surface, causing unevenness and contamination, reducing disc quality and filling the microscopic grooves or information tracks monitored by the stylus, making the disc unplayable. Sometimes. Additionally, the disk must be insensitive to changes in temperature and humidity encountered during storage and transportation.

Polyvinyl chloride resins suitable for use herein include vinyl chloride polymers, copolymers and mixtures thereof. The polyvinyl chloride resin preferably has a
It is necessary to exhibit a high heat distortion temperature of °C or higher. Suitable polymers include, for example, those manufactured by BFGoodrich Co. with a weight average molecular weight of 84,400;
Number average molecular weight 38140, T _g (glass transition temperature) 88
homopolymer of vinyl chloride, such as vinyl chloride resin at °C, or manufactured by Air Products & Chemical Inc.
There is a vinyl chloride polypropylene copolymer with a T _g of 76°C such as AP480, but it is manufactured by Great American Chemical Co.
Other polyvinyl chloride homopolymers can also be used, such as Type 550 resin from Air Products Co., Ltd. and Type 2160 resin from Air Products.

Conductive particles suitable for use in the molding compositions of this invention include highly conductive finely divided carbon black, which preferably has a low volume density to reduce filling requirements. The currently recommended product is Ketjenblack EC from Armak Co., which has an apparent volume density of 150gr/.
The average particle size is about 300 Å. This carbon black has a large surface area and intraparticle porosity measured by dibutyl phthalate absorption method, and has a high current flow efficiency between conductive particles in a non-conductive matrix. Other carbon blacks can also be used in whole or in part if they meet the electrical requirements. The higher the density of the carbon particles, the higher the degree of packing required to obtain the same electrical conductivity, for example about 35 to 40
weight%. The particle size of the conductive carbon particles is not critical, but is generally less than 500 Å to avoid the formation of grainy surfaces within the plastic matrix. The filling rate is preferably about 12 to 20% by weight of carbon black such as Ketsuen Black EC.

Selected polyvinyl chloride compositions have approximately 1.5 to 4
% by weight of stabilizer is added. Suitable stabilizers include organotin compounds such as dibutyltin β-mercaptopropionate and dibutyltin maleate, as well as lead, zinc,
There are other metal compounds derived from stearates of metals such as barium and cadmium. Epoxides, phosphites, alkylated phenols such as t-butylcatechol may also be used. The currently recommended stabilizer system is two tin salts: dibutyltin beta-mercaptopropionate, commercially available as T-35 from M&T Chemical Co., and Argus Chemical Co., Ltd. as type 275, as well as optional stabilizers such as barium cadmium lead styphosphate. Stabilizers originally function to neutralize volatile substances, especially hydrogen chloride, formed as decomposition products of polyvinyl chloride resin, but if too much stabilizer is added, it will not be absorbed by the resin, so it will not be absorbed into the resin. It may be desirable to use more than one stabilizer in the composition.

Lubricants suitable for polyvinyl chloride resins are also known and include fatty acids, fatty acid esters of alcohols, alcohol esters of polyfunctional acids, soaps such as zinc, lead or calcium stearate, stearamide, aureamide, ethylene bisstearate. There are fatty acid amides such as laamide. Again, it is necessary to use at least two lubricants to prevent lubricant leaching during the molding process. The currently recommended combination is monovalent fatty acid esters of variable molecular weight alcohols and acids, commercially available as Loxiol G-30 from Henkel International GmbH, and polyfunctional complex esters of saturated fatty acids. It is a mixture with Roxiol G-70. Lubricants such as calcium stearate can also be added.
Sufficient lubricant must be added to prevent an increase in shear heat during processing and to improve mold release of molded disks and other articles. Usually about 1-3% of the lubricant is used based on the total weight of the molding composition.

Other modifiers include plasticizers and processing aids, which can be added up to about 10% of the total weight of the molding composition. Addition of a primary plasticizer lowers the T _g and heat distortion temperature of the resin composition. These materials are compatible with polyvinyl chloride resin. Liquid primary plasticizers have a large effect on T _g and heat distortion temperature.

The total amount of liquid modifier needs to be carefully controlled. The liquid modifier must be compatible with the vinyl chloride resin so that it does not leach onto the surface.
Solid modifiers have a greater effect on the shrinkage and heat distortion temperature of the resin composition, but modulators that cannot coexist function similarly to fillers and thus have little effect on properties. Although it is necessary to have a small amount of a coexisting modulator to improve processability and suppress the stiffness-increasing effect of a large amount of conductive carbon particles in the resin, an excessive amount of the liquid, i.e., approximately 50% of the resin composition If more than 5% by weight is added, the molding composition
The T _g and heat distortion temperature decrease, resulting in undesirably high warpage and shrinkage properties of the molded article.

A liquid modifier refers to a material that is liquid at room temperature, but since a fixed low-melting point primary plasticizer also exhibits a liquid state at the mixing temperature, it is considered to belong to a liquid modifier in this case.

As noted above, the amounts of modifiers, ie, plasticizers, and processing aids in the molding compositions of this invention are determined in accordance with U.S. Pat.
less than that of the composition of No. 4151132.

The total amount of additives in the molding composition is reduced because the amount of low T _g resin such as vinyl chloride-vinyl acetate copolymer is reduced, thereby increasing the dimensional stability of the molded article.

The recommended molding composition for manufacturing conductive video discs according to this invention is
Composition for molding EC type conductive carbon particles 12-20
Weight%, dibutyltin beta-mercaptopropionate stabilizer 1.0-3.0% by weight, tin maleate stabilizer 2.0% by weight or less, Roxiol G-30 lubricant 0.25-1.5% by weight, Roxiol G-70 lubricant 0.15-0.75% by weight , up to 1% by weight of a calcium stearate lubricant, up to 5% by weight of a Skrylic processing aid, up to about 4% by weight total liquid additives, up to about 10% total fixed additives, the remainder of the composition comprising: It is a polyvinyl chloride homopolymer or a vinyl chloride/polypropylene copolymer with a T _g of about 60°C or higher.

The molding composition is prepared by first placing all of the solid ingredients in a blender, such as a Henschel mixer, and mixing until the temperature reaches approximately 49°C, then adding the liquid ingredient to cover the solid particles. prepared. Mixing continues until the temperature reaches at least about 71°C. The composition is then collected and charged into a Banbury mixer or other suitable device for melting the ingredients under shear. The composition is mixed until melted, e.g., at about 176 DEG -190 DEG C., and stored in a two-roll mill or in the form of plates or pellets. Molded products, especially video discs, are produced by conventional pressure molding, for example after preforming,
Pressure mold at ~190°C for 30-60 second cycles and remove the mold.

For this application, there must be a thin dielectric layer on the surface of the disk, which can be achieved by providing a thin film of molding composition around each conductive particle or by providing sufficient lubrication to the molding composition. The agent can be prepared by adding a small amount of the agent to the surface to form a thin film. It is also possible to apply a thin lubricant coating to the disk as a separate layer. This thin film acts as an additive dielectric coating and also serves to reduce wear on the accumulator during regeneration. One type of lubricant that has been used successfully is a methylalkylsiloxane having the formula:

However, R is an alkyl group having 4 to 20 carbon atoms, and x is an integer. These lubricants can be deposited on the disk surface by spin deposition or vapor deposition using a solution.

The present invention will now be described by way of example, but this invention is not meant to be limited to the details of this description. In the examples, parts or percentages are by weight.

Example 1 A molding composition was prepared by mixing the following ingredients in a Henschel mixer. Vinyl chloride/polypropylene copolymer AP-480 type 74.05 parts, Ketsuen Black EC type carbon particles 15 parts, Roxiol G-30
Mold lubricant 0.5 parts, Roxiol G-70 lubricant 0.25
0.3 parts of calcium stearate lubricant, commercial processing aid Acryloid K-175 from Rohm & Haas Co.
2 parts of mold, 1.5 parts of T-35 type stabilizer, 1.0 part of liquid dibutyltin maleate stabilizer Mark 275, 1.0 part of commercial barium lead steerate stabilizer Mark Q232B from Argus Chemical Company, Rohm & Co.・Liquid plasticizer epoxidized soybean oil Paraplex G-62 type 1.0 commercially available from Haas
Commercially available esterified montan wax lubricant Wax Type E from Hoechst Co.
0.4 parts, Velsicol Chemical Company
Benzoflex, a glyceryl benzoate solid plasticizer commercially available from Chemicol Corp.
1.0 part of Type S404 and 2.0 parts of Unichlor 70AX, a chlorinated paraffin wax solid modifier commercially available from Neville Chemical Co.

Mixing was continued until the temperature reached approximately 87.8°C, and the mixture was cooled and fed to a plastic extruder to form a pelletized composition. The aforementioned U.S. Patent No.
176.7 using the metal pressing machine described in the specification of No. 3842194.
Video disks approximately 30.5 cm (12 inches) in diameter were pressure molded from this PET on a 36 second cycle at 0.degree.

Place this disk on the central axis and approximately 37.8 to 54.4 degrees Celsius.
Shrinkage tests were carried out by placing the specimens in an oven at various temperatures for various times. When the diameter of the disk was measured before and after heat treatment, as shown in Figure 1, the shrinkage increased as the temperature increased, but stabilized after about 120 hours.
All disks tested had shrinkage of less than about 1.27 mm.

For comparison, a disk molded with the molding composition described in Example 1 of the aforementioned U.S. Pat.
When heated at ℃ for 24 hours, a 12-inch disk
It showed a shrinkage of 2.5-2.7 mm.

Example 2 Using the composition of Example 1, several trials were run with the addition of increasing amounts of Santicizer type 711, a liquid phthalate modulator commercially available from Monsanto Corp. disk
When the shrinkage was measured by heating test at 54.4° C. for 24 hours, the shrinkage increased significantly with the amount of liquid additive added, as shown in FIG.

Example 3 A molding composition was prepared in the same manner as in Example 1 using GAC550 type polyvinyl chloride homopolymer instead of the polyvinyl chloride/polypropylene copolymer of Example 1.

Example 1: Prototyping a video disc from this composition
When tested in the same manner as above, it showed a shrinkage of approximately 0.6 mm.

Example 4 A molding composition similar to that of Example 1 was prepared substituting Gutdrich's polyvinyl chloride homopolymer having the T _g at 88° C. as described above as the resin.

Example 1: Video disk molded from this composition
When tested in the same manner as above, the shrinkage was approximately 0.3 mm.

Example 5 76.5% of the polyvinyl chloride homopolymer of Example 4, Ketschen Black EC type 15.0%, Roxiol G-30 type lubricant 0.75%, Roxiol G
−70 type lubricant 0.25%, calcium stearate lubricant 0.5%, β-mercaptopropionate dibutyltin stabilizer 2.0%, Mark 275 type tin maleate stabilizer
1.0%, and Santeisizer, a commercially available primary phthalate liquid plasticizer from Rohm and Haas.
A molding composition was prepared containing 3.0% Type 711 and 2.0% of the solid acrylic modifier Acryloid Type K-147.

Example 1: Prototyping a video disc from this composition
When a similar test was conducted, a shrinkage of approximately 0.6 mm was obtained.

Comparative Example A: Omitting the tin maleate stabilizer and using 0.75 parts of G-30 and 1.0 parts of calcium stearate lubricant,
Epoxidized soybean oil was omitted and replaced with 2.0 parts of polymer ester liquid plasticizer Kodaflex NP-10 type.
A molding composition similar to that shown in FIG. 1 was prepared by adding 3.0 parts of dicyclohexyl phthalate, a solid primary plasticizer which is liquid at the processing temperature. The effective liquid content of this composition was 6.0%.

Example 1: Prototyping a video disc from this composition
A shrinkage of about 1.9 mm was obtained by testing in the same manner as above.

Comparative Example B The polyvinyl chloride resin of Example 3, 15 parts of Kettien Black EC type carbon particles, 0.5 part of G-30 and G-
0.25 part of 70, 1 part of calcium stearate, T-
A molding composition was prepared as in Example 1 using 2 parts of Type 35 stabilizer, 2 parts of K-175 and 7 parts of liquid plasticizer Kodaflex NP-10. The liquid content of this composition was 7%.

Example 1: Prototyping a video disc from this composition
A similar test was conducted and a shrinkage of approximately 1.8 mm was obtained.

[Brief explanation of drawings]

Figure 1 is a chart showing the shrinkage vs. time characteristics at various temperatures of disks molded from the molding composition of this invention, and Figure 2 shows the shrinkage effect when a liquid modifier is added to the molding composition of this invention. This is a chart showing.

Claims (1)

[Scope of Claims] 1. An information recording medium suitable for use with a reproducing needle and reproducing a signal occupying a bandwidth of at least several MHz when a relative movement of a required speed is established between the recording medium and the reproducing needle. and contains fine conductive particles.
comprising a disk of plastic material having a volume resistivity of less than or equal to about 500 Ω-cm at 900 MHz and constituted by an information pattern on its surface having dimensions adapted to reproduce a signal of said bandwidth upon establishment of said motion of said velocity; and conductive carbon black particles, about 1.5 to 4% by weight of a stabilizer for polyvinyl chloride resin, and about 1 to 3% by weight of at least two lubricants for polyvinyl chloride resin. Characteristically, in order to provide dimensional stability and processability, the molding composition contains not more than 10% by weight of a plasticizer for polyvinyl chloride resin. and processing aids and the remainder a polyvinyl chloride resin having a T _g of at least 60°C, present in an amount of up to about 5% by weight as a liquid additive compatible with the resin; , a stabilizer, a lubricant, a plasticizer and a processing aid are uniformly dispersed together with the resin.